A composite ceramic green sheet which is a composite of at least two portions having different compositions has been hitherto known (see Japanese Patent No. 2535617 (Page 1 and FIG. 12)).
Japanese Patent No. 2535617 (Page 1 and FIG. 12) discloses, as one of manufacturing processes of ceramic green sheets, a technique for obtaining a composite ceramic green sheet by casting first and second slurries using a doctor blade method in the state where the first and second slurries are in contact with each other and in parallel to each other (see Claims 1 and FIG. 12).